The optical principle of the upright metallographic microscope is based on geometric optics and reflection imaging technology, and its core is to magnify the microstructure of metal materials through a precise optical system. Its working principle is that the light emitted by the light source is focused by a condenser lens and illuminates the surface of the sample in a vertical or oblique manner. Due to its opaque nature, the metal sample is imaged only by the reflected light on the surface. The reflected light is collected by the objective lens to form an inverted real image, which is then magnified twice by the eyepiece to form a virtual image, and finally presented to the observer's field of view. In this process, the numerical aperture of the objective lens and the wavelength of the light jointly determine the resolution, while the application of the prism group ensures that the image direction is consistent with the actual direction of the sample, overcoming the limitations of traditional inverted imaging.

The optimization of imaging quality requires coordinated regulation from both hardware configuration and operating parameters. On the hardware level, it is necessary to use high numerical aperture objective lenses and achromatic design eyepieces to reduce aberrations and improve resolution; Equipped with a Kohler illumination system, the incident light angle can be controlled by adjusting the aperture stop, which can enhance the contrast of grain boundaries, especially suitable for dark field observation. At the software level, the choice of lighting method is crucial: reflective lighting is suitable for observing metal grains, while polarized lighting can enhance the recognition of anisotropic phases. When operating, it is necessary to follow the principle of "low magnification positioning high magnification focusing". First, adjust the focal length roughly with a 10 x objective lens, and then switch to a 50 x or 100 x objective lens for fine adjustment to avoid crushing the sample; At the same time, adjusting the observation range through the field of view aperture can reduce the internal reflection interference of the lens barrel.

During the image acquisition phase, it is necessary to optimize parameters by combining dynamic range and signal-to-noise ratio. For example, using high dynamic range cameras can avoid overexposure or underexposure, while low-noise sensors can improve detail restoration. During post-processing, using image analysis software for grayscale correction and contrast enhancement can further highlight grain boundaries or phase boundary features. In addition, regular calibration of the system ruler to ensure the accuracy of magnification is the basis for quantitative analysis of grain size or phase proportion.